Question

if the radius of a circle is decreased by 20% find the percentage decreasing in its area
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Answer 1

Answer:

hiiii

your answer is here !

Step-by-step explanation:

Area of Square = Pi* radius^2

New Radius = 4/5 * old radius

so new area = (4/5)^2 old area => 16/25 of old area => 64% old area

follow me !

Answer 2

Answer:

36%

Step-by-step explanation:

Let r be the radius of a circle,

The the area of the circle,

$A_1=\pi (radius)^2 = \pi(r)^2$

After decreasing the radius by 20%,

New radius = 80% of r = 0.8r,

Thus, new area would be $A_2=\pi(0.8r)^2$

Hence, the decreasing change rate in area,

$\frac{A_1-A_1}{A_2}\times 100$

$=\frac{\pi(r)^2 - \pi(0.8r)^2 }{\pir^2}\times 100$

$=\frac{r^2 - 0.64r^2}{r^2}\times 100$

$=(0.10 - 0.64)\times 100$

= 36%